The present invention relates to a ventilation system for ventilating the inside of the compartment of an automobile or building and, more particularly, to an improvement in an inside air releasing system for releasing the contaminated air in the compartment (as will be called the "inside air") to the outside.
One ventilation system of the prior art is constructed, as disclosed in Japanese Utility Model Publication No. Sho 62-9130 or Japanese Patent Laid-Open No. Sho 59-63221, of: a mouth frame having an inside air outlet for releasing the inside air to the outside of a compartment; and a one-way valve adapted to come into abutment against the peripheral edge of said inside air outlet acting as a valve seat, at times other than the time of releasing the inside air to the outside, thereby to close said inside air outlet and apart from said valve seat, at the time of releasing the inside air to the outside, thereby to open said inside air outlet in the releasing direction only.
This one-way valve is formed into a reed larger than said inside air outlet and arranged on the outer side of said mouth frame. The upper end of the one-way valve is attached just above the inside air outlet so that its substantial entirety excepting said upper end can swing on said attached portion. And, the one-way valve is brought by its own weight into abutment against the peripheral edge of the inside air outlet at times other than the time of releasing the inside air to the outside thereby to close the inside air outlet. When, however, the pressure difference (which is caused by a vacuum generated on the surface of a car body at the running time and acted upon the one-way valve) between the inside and outside of the compartment exceeds the weight of the one-way valve, the one-way valve is swung apart from the peripheral edge of the inside air outlet to the outside to open the inside air outlet only in the direction to release the inside air to the outside.
The ventilation system thus constructed is mounted for use on the car, for example. Since the compartment of the car is relatively small and is liable to be contaminated with the smoke of cigarette and the breathing of the passengers, the ventilation system is required to have a performance to release the inside air quickly to the outside. In the prior art, therefore, the one-way valve has its thickness and accordingly its weight reduced so that it can open the aforementioned inside air outlet even under a small pressure difference thereby to release the contaminated inside air efficiently.
If, however, the one-way valve is thinned to become lighter as in the prior art, the force to bring it into abutment against the valve seat for closing the inside air outlet is reduced, and its edge become liable to be deformed. As a result, a clearance is established between the one-way valve and the valve seat, thus causing a defect that the sealing properties of the inside air outlet are deteriorated. Since, moreover, the one-way valve is liable to bound, if light, under the influences of the vibrations at the running time of the car, it may open the inside air outlet widely. If the inside air outlet thus has its sealing properties deteriorated or is uselessly opened, the outside contaminated air containing sand, dust, smoke and/or a bad smell (as will be called the "outside air") may flow back from the inside air outlet into the car compartment to make the passenger uncomfortable. This has also been a problem to be solved in the prior art. This back-flow phenomena prominently occur especially when the car runs on a place with a cloud of sand. Thus, numerous car users have desired such a ventilation system as can close the aforementioned inside air outlet in a reliably sealed state.